U.S. patent application number 13/764111 was filed with the patent office on 2015-07-09 for variable thickness heat pipe.
This patent application is currently assigned to Google Inc.. The applicant listed for this patent is Google Inc.. Invention is credited to William Riis Hamburgen, Felix Jose Alvarez Rivera, James Tanner.
Application Number | 20150192369 13/764111 |
Document ID | / |
Family ID | 53494892 |
Filed Date | 2015-07-09 |
United States Patent
Application |
20150192369 |
Kind Code |
A1 |
Rivera; Felix Jose Alvarez ;
et al. |
July 9, 2015 |
VARIABLE THICKNESS HEAT PIPE
Abstract
In one aspect, a cooling system is provided for use in computing
devices, such as laptops, cell phones, and tablet computers. The
cooling system includes a heat spreader coupled to a radiator via a
heat pipe having a midline. The heat pipe includes a first end
portion longitudinally extending along the midline, a second end
portion longitudinally extending along the midline, and a
mid-portion longitudinally extending along the midline. The
mid-portion is located between the first end portion and the second
end portion and it has a thickness that is greater than the
thicknesses of both the first portion and the second portion
thereby reducing the overall thermal resistance of the heat
pipe.
Inventors: |
Rivera; Felix Jose Alvarez;
(San Jose, CA) ; Tanner; James; (Los Gatos,
CA) ; Hamburgen; William Riis; (Los Altos,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc.; |
|
|
US |
|
|
Assignee: |
Google Inc.
Mountain View
CA
|
Family ID: |
53494892 |
Appl. No.: |
13/764111 |
Filed: |
February 11, 2013 |
Current U.S.
Class: |
165/104.19 |
Current CPC
Class: |
G06F 1/20 20130101; F28D
15/0233 20130101; H01L 21/4882 20130101; H01L 2924/00 20130101;
H01L 23/427 20130101; H01L 2924/0002 20130101; F28D 15/04 20130101;
H01L 2924/0002 20130101; H05K 7/20663 20130101; G06F 1/203
20130101; F28D 15/0275 20130101; H05K 7/20336 20130101; H01L 23/467
20130101 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Claims
1. A cooling assembly, comprising: a heat spreader; a radiator; and
a heat pipe coupling the heat spreader and the radiator, the heat
pipe having a midline therealong, the heat pipe including: a first
end portion extending longitudinally along the midline and
connected to the heat spreader, the first end portion having a
first thickness, a second end portion extending longitudinally
along the midline, the second end portion being connected to the
radiator, the second end portion having a second thickness, and a
mid-portion extending longitudinally along the midline, the
mid-portion being located between the first end portion and the
second-end portion, and the mid-portion having a third thickness
that is greater than the first thickness and the second
thickness.
2. The cooling assembly of claim 1, wherein the first end portion,
the second end portion, and the mid-portion have a uniform
width.
3. The cooling assembly of claim 1, wherein the first end portion,
the second end portion, and the mid-portion are arranged
co-linearly.
4. The cooling assembly of claim 1, wherein the first thickness is
equal to 1 L mm, the second thickness is equal to 1.5 L mm, and the
third thickness is equal to 1.3 L mm, wherein L is an integer
greater than or equal to 1.
5. The cooling assembly of claim 1, wherein the heat pipe further
includes a casing having a uniform wall thickness and a wick
enclosed in the casing.
6. The cooling assembly of claim 1, wherein the heat pipe further
includes a casing having a variable wall thickness and a wick
enclosed in the casing, wherein the casing has a greater wall
thickness in the mid-portion of the heat pipe than in the either
one of the first end portion and the second end portion.
7. The cooling assembly of claim 1, wherein: the first end portion
is disposed on a surface of the heat spreader; the first end
portion extends substantially up to an edge of the heat spreader
where the surface ends; and the mid-portion juts below the edge of
the heat spreader starting at a location on the heat pipe where the
first end portion ends and the mid-portion begins.
8. The cooling assembly of claim 1, wherein the second thickness of
the second end portion is greater than the first thickness of the
first end portion.
9. An apparatus comprising: an enclosure having a first face and a
second face opposite the first face; a heat-generating component
disposed inside the enclosure between the first face and the second
face; a radiator disposed inside the enclosure between the first
face and the second face; a heat spreader that is in thermal
contact with the heat generating component, the heat spreader being
disposed between the heat generating component and the top face;
and a heat pipe including: a first end portion extending
longitudinally along the midline and connected to the heat
spreader, the first-end portion being disposed on the heat spreader
and between the heat spreader and the first face, the first end
portion having a first thickness, a second end portion extending
longitudinally along the midline, the second end portion being
connected to the radiator, and the second end portion having a
second thickness, and a mid-portion extending longitudinally along
the midline, the mid-portion connecting the first end portion and
the second-end portion, the mid-portion having a third thickness
that is greater than either one of the first thickness and the
second thickness.
10. The apparatus of claim 9, wherein the first end portion, the
second end portion, and the mid-portion have a uniform width.
11. The apparatus of claim 9, wherein the first end portion, the
second end portion, and the mid-portion are co-linear.
12. The apparatus of claim 9, wherein the first thickness is equal
to 1 L mm, the second thickness is equal to 1.5 L mm, and the third
thickness is equal to 1.3 L mm, wherein L is an integer greater
than or equal to 1.
13. The apparatus of claim 9, wherein the heat pipe further
includes a casing having a uniform wall thickness and a wick
enclosed in the casing.
14. The apparatus of claim 13, wherein the casing has a greater
wall thickness in the mid-portion of the heat pipe than in the
either one of the first end portion and the second end portion.
15. The apparatus of claim 9, wherein: the first end portion is
disposed on a surface of the heat spreader; the first end portion
extends substantially upto an edge of the heat spreader where the
surface ends; and the mid-portion juts below the edge of the heat
spreader starting at a location on the heat pipe where the first
end portion ends and the mid-portion begins.
16. The apparatus of claim 9, wherein the second thickness of the
second end portion is greater than the first thickness of the first
end portion.
17. An apparatus comprising: an enclosure having a first face and a
second face opposite the first face; a circuit board disposed
between the first face and the second face; one or more integrated
circuits mounted on the circuit board; a heat spreader disposed on
at least some of the one or more integrated circuits; a radiator
disposed inside the enclosure between the first face and the second
face; and a heat pipe disposed between the first face and the
second face, the heat pipe having a midline therealong, the heat
pipe including: a first end portion connected to the radiator, the
first end portion extending longitudinally along the mid-line; a
second end portion connected to the heat spreader, the second end
portion extending longitudinally along the mid-line; and a
mid-portion connecting the first end portion and the second
portion, the mid-portion extending longitudinally along the
mid-line, and the mid-portion extending further towards a surface
of the circuit board than the first end portion and the second end
portion.
18. The apparatus of claim 17, wherein the mid-portion extends a
same distance away from the surface of the circuit board as the
first end portion and the second end portion.
19. The apparatus of claim 17, wherein the mid-portion extends a
same distance in a direction parallel to the surface of the circuit
board as the first end portion and the second end portion.
20. The apparatus of claim 17, wherein the heat pipe further
includes: a casing that defines the first end portion, the second
end portion, and the mid-portion, the casing having a uniform wall
thickness, and a wick enclosed in the casing.
Description
BACKGROUND
[0001] Thin-profile devices such as laptops, tablets, and smart
phones are becoming ever lighter and smaller. Such devices
ordinarily include cooling systems that dissipate heat generated by
their internal components. The cooling systems may include heat
pipes, radiators, and cooling fans. In general, the thinner the
profile of a device, the less room there is in the device's
enclosure for those cooling systems to fit in. Thus, cooling
systems that are used in thin-profile devices need to possess at
least two characteristics that are somewhat at odds with one
another, namely they should fit into tight spaces, and they should
have sufficient cooling capacity in order to prevent the devices
from overheating. Striking an appropriate balance between size and
cooling capacity of a cooling system is one of the challenges
designers of thin-profile devices face.
SUMMARY
[0002] In one aspect, a cooling system is provided that is suitable
for use in thin-profile portable devices. The cooling system
includes a heat spreader, a radiator and a heat pipe coupling to
the heat spreader and the radiator. The heat pipe may have a
midline therealong. The heat pipe includes a first end portion
extending longitudinally along the midline, a second end portion
extending longitudinally along the midline, and a mid-portion
extending longitudinally along the midline. The first end portion
connects to the heat spreader and has a first thickness. The second
end portion connects to the radiator and has a second thickness.
The mid-portion may be located between the first end portion and
the second-end portion, and has a third thickness that is greater
than the first thickness and the second thickness.
[0003] In one example, the heat pipe may further include a casing
having a variable wall thickness and a wick enclosed in the casing.
The casing has a greater wall thickness in the mid-portion of the
heat pipe than in the either one of the first end portion and the
second end portion. In another example, the first end portion may
be disposed on a surface of the heat spreader. Starting at a
location on the heat pipe where the first end portion ends and the
mid-portion begins, the mid-portion juts below the edge of the heat
spreader. The first end portion extends substantially up to an edge
of the heat spreader where the surface ends.
[0004] In another aspect, an apparatus is provided that includes an
enclosure having a first face and a second face opposite the first
face, a heat-generating component disposed inside the enclosure
between the first face and the second face, and a radiator disposed
inside the enclosure between the first face and the second face.
The apparatus includes a heat spreader that is in thermal contact
with the heat generating component. The heat spreader is disposed
between the heat generating component and the top face. The
apparatus also includes a heat pipe. The heat pipe includes a first
end portion extending longitudinally along the midline, a second
end portion extending longitudinally along the midline and a
mid-portion extending longitudinally along the midline. The
first-end portion connects to the heat spreader and may be disposed
on the heat spreader between the heat spreader and the first face.
Connected to the radiator is the second end portion. The first end
portion has a first thickness and the second end portion has a
second thickness. The mid-portion that connects the first end
portion and the second-end portion has a third thickness greater
than either one of the first thickness and the second
thickness.
[0005] In yet another aspect, an apparatus is provided that
includes an enclosure having a first face and a second face
opposite the first face. A circuit board may be disposed between
the first face and the second face. One or more integrated circuits
may be mounted on the circuit board. A heat spreader may be
disposed on at least some of the one or more integrated circuits.
The apparatus includes a radiator disposed inside the enclosure
between the first face and the second face and a heat pipe disposed
between the first face and the second face. The heat pipe has a
midline therealong. The heat pipe includes a first end portion
connected to the radiator, a second end portion connected to the
heat spreader and a mid-portion connecting the first end portion
and the second portion. The first end portion and second end
portion extend longitudinally along the mid-line. The mid-portion
extends longitudinally along the mid-line, and may extend further
towards a surface of the circuit board than the first end portion
and the second end portion.
[0006] In one example, the heat pipe further includes a casing that
defines the first end portion and a wick enclosed in the casing.
The second end portion, and the mid-portion, the casing having a
uniform wall thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1A depicts a perspective view of a cooling system in
accordance with one aspect of the disclosure.
[0008] FIG. 1B depicts a top view of the cooling system of FIG.
1A.
[0009] FIG. 1C depicts a perspective view of a heat pipe the
cooling system of FIG. 1 in accordance with one example.
[0010] FIG. 2A depicts a top view of the heat pipe of the cooling
system of FIG. 1A in accordance with another aspect of the
disclosure.
[0011] FIG. 2B depicts a side view of the heat pipe of FIG. 2A.
[0012] FIG. 2C depicts a side view of the heat pipe of FIG. 2A.
[0013] FIG. 2D depicts a side view of the heat pipe of FIG. 2A.
[0014] FIG. 2E depicts a cross-sectional view of the heat pipe of
FIG. 2A.
[0015] FIG. 2F depicts another cross-sectional view of the heat
pipe of FIG. 2A.
[0016] FIG. 3A depicts a computing device that might utilize the
cooling system of FIG. 1A.
[0017] FIG. 3B depicts a cross-sectional view of the computing
device of FIG. 3A.
[0018] FIG. 3C depicts another cross-sectional view of the
computing device of FIG. 3A.
DETAILED DESCRIPTION
[0019] FIGS. 1A-B depict a cooling system 100 in accordance with
aspects of the disclosure. FIG. 1A depicts a perspective view of
the system 100 and FIG. 1B depicts a top down view of the system
100. As illustrated, the cooling system 100 includes a heat
spreader 110 coupled to a radiator 130 via a heat pipe 120. The
heat spreader 110 may be a metal plate, or any other heat-exchanger
that is used to connect the cooling system 100 to a heat source.
The radiator 130 may be any type of radiator or heat sink. In this
example, the radiator 130 may be a fin pack, such as the one
described in U.S. application Ser. No. 13/438,293 titled "Active
Cooling Fin Pack," which is herein incorporated by reference.
[0020] The heat pipe is a device that transports heat from the heat
spreader 110 to the radiator 130. The heat pipe 120 may have a
first end portion 122, a mid-portion 124, and a second end portion
126. The mid-portion 126 is thicker than both end portions.
Configuring the heat-pipe 120 to have thinner end portions enables
it to be stacked over device components inside device enclosures
that have limited vertical clearance. At the same time, having a
thicker mid-portion enables the heat pipe 120 to retain a
sufficiently low thermal resistance to remove heat from the
device's components at a sufficient rate.
[0021] In one aspect, the heat pipe 120 may have a variable
thickness. As illustrated in FIG. 1C, the end portion 122 may have
a thickness T1, the end portion 126 may have a thickness T2, and
the mid-portion may have a thickness T3, wherein
T1.noteq.T2.noteq.T3. In this example, T1=1.0*L mm, T2=1.3*L mm,
and T3=1.5*L mm, wherein L is an integer greater than or equal to
1. The mid-portion 120 may have an arced shape, or alternatively,
it may have a substantially flat shape.
[0022] In another aspect, the end portion 122, the mid-portion 124,
and the end portion 126 may extend longitudinally along a midline
M. Although in this example, as shown in FIG. 1C, the end portions
122 and 126, and the mid-portion 124 are arranged along the midline
so as to define J-shape, in other examples, the end portions and
the mid-line may be arranged in the shape of a straight line. In
the latter examples, the mid-line M is a straight line and not a
curved line, as is the case in this example.
[0023] FIGS. 2A-F depict the heat pipe 120 in accordance with an
example where the mid-potion and end portions are arranged in a
straight line. Specifically, FIG. 2A depicts a top-down view of the
heat pipe 120 illustrating that the heat pipe 120 may have a
substantially uniform width W. FIG. 2B depicts a first side view of
the heat pipe 120 showing that the heat pipe 120 may have a
variable thickness. As illustrated, the end portion 122 may be
connected to a surface 112 of the heat spreader 110 and it may
extend substantially up to an edge 114 of the surface. The
mid-portion 124 may begin where the end portion 122 ends.
Furthermore, the mid-portion 124 may jut down below the edge 114
starting at the location where the mid-portion 124 begins.
[0024] FIGS. 2C-D depict side views of the heat pipe 120
illustrating that the end portion 126 may be thicker than the end
portion 124. Furthermore, as noted above, FIGS. 2C-D illustrate
that the heat pipe 120 may have a uniform width with the end
portions 124 and 126, and the mid-portion 124 having substantially
the same width. In other examples, however, the end portions 124
and 126 and the mid-portion 124 may have different widths.
[0025] FIG. 2E-F depict cross-sectional views of the heat-pipe 120
in accordance with aspects of the disclosure. FIG. 2E depicts a
cross-sectional view of the heat pipe 120 along the midline M and
FIG. 2F depicts a cross-sectional view of the heat pipe 120 along
an axis C. As illustrated, the heat pipe 120 includes a casing 210,
a wick 220 disposed inside the casing, and a working fluid (not
shown), also disposed inside the casing 210. In one aspect, the
casing may be a tube-like metal structure having circular,
rectangular, or any other shape of cross-section. In another
aspect, the casing 210 may be a monolithic structure that defines
all of the end portion 122, the mid-portion 124, and the end
portion 126. Although in this example, the casing has a uniform
wall thickness D, in other examples, the casing may have a variable
wall thickness. For example, the end portions of the heat-pipe 120
may have thinner walls than the mid-portion 124. The wick 220 may
be a metal mesh, sinder, or any other type of wick suitable for use
in heat pipes. In this example, the wick may be a 6 mm.times.160 mm
wire mesh wick.
[0026] In operation, the wick 220 may use capillary action to move
the working fluid from the end portion 126 to the end portion 122.
Once at the end portion 124, the fluid may be evaporated by heat
received from the heat spreader 110 and travel back to the end
portion 126, driven by a pressure differential between the end
portions 122 and 126. By the time the vapor reaches the end portion
126, it is expected to have liquefied and be ready to be
transported back to the end portion 122 for a repetition of the
same cycle.
[0027] FIG. 3A depicts an example of a device 300 where the cooling
system 100 may be used. In this example, the device 300 is a tablet
computer, but in other examples, the device 300 may be a smart
phone, a laptop, or any other computing device. FIG. 3B depicts a
cross-sectional view of the device 300 along the midline M. The
device 300 includes an enclosure 310, a system board 320, an
integrated circuit 330, the heat spreader 110, the fan 140, and the
radiator 130.
[0028] The enclosure 310 may include a face 312, a face 314, a
side-wall 316, and a side-wall 318. The face 312 may include a
display screen (e.g., LCD), a keyboard, a mouse pad, or any other
interface device. Alternatively, the face 312 may be a plastic or
metal panel, without any interface components built-in, that is
used to protect the device 300 from physical damage. Similarly, the
face 314 may include a display screen (e.g., LCD), a keyboard, a
mousepad, or any other interface device. Alternatively, the face
314 may be a plastic or metal panel, without any interface
components built-in, that is used to protect the device 300 from
physical damage. In this example, the face 314 includes an LCD
screen and the face 312 is a plastic panel.
[0029] The circuit board 320 may be a motherboard, a network
interface board, or any other substrate base on which at least one
of the radiator 130 and the integrated circuit 130. The integrated
circuit 330 may be a CPU, GPU, another integrated circuit, or any
other heat source that is part of the device 300. The integrated
circuit 330 may be stacked on the circuit board 320, and the heat
spreader 110 may be stacked on the integrated circuit 330.
Similarly, the fan 140 may be stacked on the circuit board 320 and
the radiator 130 may be placed atop the fan 140.
[0030] Thus, two separate stacks, separated by some distance from
one another, may protrude from the circuit board 320. The heat pipe
120 may be placed atop the two stacks, with the mid-portion 124
occupying free space between the two stacks. The mid-portion 126
may extend towards the system board 320 below the end portions 122
and 126 in order take advantage of free space that is available
space between the two stacks.
[0031] FIG. 3C illustrates a cross-section of the device 100 along
an axis C. Together, FIGS. 3B and 3C illustrate that the midline M
of the heat pipe 120, the faces 312 and 314, and the circuit board
320 may be substantially parallel to one another. Furthermore, the
mid-portion 124 and the end portions 122 and 126 may extend a
different distance towards the circuit board 320 and the face 314
while extending substantially the same distance towards the face
312. Similarly, as the mid-portion 124 and the end portions 122 and
124 may extend the same distance in the directions parallel to the
circuit board 320 and the faces 312-314.
[0032] In one aspect, having a thicker mid-portion increases the
cooling capacity of the cooling system 100 by reducing the heat
pipe's 120 thermal resistance. In general, the thinner the heat
pipe 120, the greater its thermal resistance. On the other hand,
the thicker the heat pipe 120, the more difficult it is to fit the
heat pipe inside the enclosure 310. In that regard, the thickness
the end portion 122 may be reduced so that it fits in the space
between the heat spreader 110 and the face 312. Reducing the
thickness of only a limited portion of the heat pipe 120 (e.g., end
portion 122), while keeping the mid-portion 124 thicker than the
mid-portion 122, may help maintain the thermal resistance of the
heat pipe 120 at an acceptable level.
[0033] In another aspect, the rate at which the cooling system 100
dissipates heat may be optimized by enlarging the radiator 130 at
the cost of making the end portion 126 thinner. Making the end
portion 126 thinner may be necessary, if the thickness of the
radiator 130 were to be increased, because of limited space
available between the circuit board 320 and the face 312. On one
hand, making the end portion thinner than the mid-portion 124, may
increase the thermal resistance of the heat pipe 120 thereby
causing it to remove heat from the integrated circuit 330 at a
slower rate. On the other hand, however, in instances where the
radiator 130 is a fin pack such as the one discussed above,
increasing the size of the radiator may raise the rate at which
heat is removed by the cooling system 100 from the integrated
circuit 330. The increase in the heat dissipation rate resulting
from the enlargement of the radiator 130 may offset some of the
negative impact on the heat dissipation rate of the system 100
resulting from thinning the end portion 130. This is especially so
because the fin pack features can be generally adjusted to increase
their surface area to improve the heat transfer rate.
[0034] FIGS. 1A-3C are provided as examples. Although in the above
examples, the heat pipe 120 is depicted as being placed atop the
radiator 130, in other examples it may be inserted into the
radiator or placed underneath the radiator. As these and other
variations and combinations of the features discussed above can be
utilized without departing from the subject matter as defined by
the claims, the foregoing description of exemplary aspects should
be taken by way of illustration rather than by way of limitation of
the subject matter as defined by the claims. It will also be
understood that the provision of the examples described herein (as
well as clauses phrased as "such as," "e.g.", "including" and the
like) should not be interpreted as limiting the claimed subject
matter to the specific examples; rather, the examples are intended
to illustrate only some of many possible aspects.
* * * * *